building stand-alone practice areas that contain sound

[SoliMusicScottSteele]

I'm completely new to this world of studio design, sound reduction, noise control, etc... I work for a small business that teaches music lessons to private students in Southern California - we are just South of Los Angeles (in the U.S.A.)

I am looking for any guidance with planning cost-effective methods of drawing-up and building at least two booths for stand-alone music practice rooms that will contain as much sound as possible.

I intend to build several practice areas to keep inside of a large warehouse with 20 foot-tall ceilings, concrete walls and concrete floors.

Each practice area is intended to have interior dimensions of at least 9 feet wide, at least 6 feet long, and at least 8 feet high - to be built with at least four walls and a ceiling

[Soundman2020]

Hi there "SoliMusicScottSteele". Welcome!

What you are talking about is commonly called "acoustic isolation", or just plain "isolation". Some people call it "soundproofing", but that is not correct: technically, it is impossible to "soundproof" anything, since any sufficiently loud sound will penetrate any conceivable barrier. Also, some people use the word "soundproofing" in a totally different and unrelated way, to refer to the acoustic treatment that goes inside a room, to make it sound good. That has nothing at all to do with isolating the room, so that sound does not get in and out. So we prefer to no use "soundproofing" here, and just call it what it is: isolation.

I am looking for any guidance with planning cost-effective methods of drawing-up and building at least two booths for stand-alone music practice rooms that will contain as much sound as possible.

In order to do that, you first need to define what you mean by "contain as much sound as possible" in technical terms. That's a subjective terms, and not something that can be measured or designed for. What I call "well isolated", you might consider "totally insufficient", while somebody else might call it "way overkill"

In other words, you need to figure out how many decibels of isolation you need. It's not hard to do: you just need a simple hand-held sound level meter to measure how loud a typical rehearsal session is, and how quite you want it to be outside the room. Subtract B from A, and you have the answer to the question: how many decibels of isolation do you need?

With that answer, you can then look at the materials, techniques, and methods for building walls that will give you that much isolation. You can compare several such techniques/materials to find one that fits your budget and uses materials that are easily available in your area.

Each practice area is intended to have interior dimensions of at least 9 feet wide, at least 6 feet long, and at least 8 feet high -

Those are pretty small rooms! That's about right for one single person with his own instrument, and it will sound pretty terrible in there: small rooms sound bad, no matter what you do to treat them. The smaller they are, the worse they sound. And also, the smaller they are, the more treatment they need in order to help them not sound so terrible. A large room needs very little treatment, proportionally, to sound good. A small room needs a huge amount, and even then won't sound good.

So if you have the space, build them bigger! Especially if you have 20 feet of height why limit the rooms to just 8 feet?

to be built with at least four walls and a ceiling

Yes, it is absolutely necessary to build four walls and a ceiling, but it's a bit more complex than that. You also need to take into account the doors, windows, electrical system, and HVAC system. HVAC is a major issue in studios, and is something that first-time builders often forget about completely, or think about a bit but then erroneously come to the conclusion that it isn't important, or that they won't need it... Big mistake! It's a key part. Critical. You need to be designing that right from the start, along with all the rest.


- Stuart -

[SoliMusicScottSteele]

Soundman2020
thank you very much for helping me begin to think through this project with some guidance.

I found a general decibel chart from GCAudio website that I'm assuming is relatively accurate for the decibel levels that we generally have (from the loudest reference point at the instruments).
Sound Levels of Music (only including instruments that we commonly have in the studio):
Normal piano practice 60 -70dB
Piano Fortissimo 84 - 103dB
Violin 82 - 92dB
Cello 85 -111dB
Oboe 95-112dB
Flute 92 -103dB
Clarinet 85 - 114dB
French horn 90 - 106dB
Trombone 85 - 114dB

I would love to achieve a 30 decibel level just outside the room, which would indicate that subtracting 30dB (desired level) from 105dB (my roughly estimated, level of decibels that is frequently achieved by our musicians), then I would be seeking 75dB of sound isolation.


Having put some thought into what you were saying about size of the rooms, I started considering building somewhat larger stand-alone units (adding a couple feet of width and length), and extending them upwards several feet, to create more open air for sound to dissipate in, and help improve internal acoustics.

Then I started considering costs, and balked a bit, and reconsidered modifying our preexisting room that is 9.5 feet wide, and 17.5 feet long, with a single door close to one end of the room. It has 2 layers of sheet rock on each side of the framing, contains cheap insulation that is generic to most office spaces,
and has a ceiling that is about as solid as a sheet of paper, with ceiling joists about every 6 feet, and a 2 foot by 4 foot grid-network of sheetmetal framing that suspends the electrical wiring, styrofoam-like panels, and has HVAC intake and outtake vents on each end of the room. One wall is up adjacent to our warehouse, and it is not at all critical to prevent sound from flooding into that space.

I am considering the option of adding a wall in the middle of the room, to subdivide it into 2 identical practice areas, building a door frame for the newly portioned-off room, wiring a lightswitch for that room, employing the preexisting HVAC system that would be fine untouched other than treating for sound isolation, and then bulking up all of the walls by using something along the lines of:
Roxul "safe n sound insulation" and sheetrock with Green Glue for all the walls, which are both available in my neighborhood at retailers, although I would be happy to consider other options. I have no idea yet as to how to discern the level of sound isolation I will achieve from different materials and methods, and what is the best method of laying out all of my construction, and especially am clueless about the ceilings and floors, and what doorways I should look into, especially that will provide a window for people to monitor what is happening in the rooms (would need to be at least 1 square foot large (any rectangular shape would suffice).

I would love to hear more feedback, constructive criticism, direction to specific materials, construction design approaches, or anything else that I should take into account.

Thanks again for interacting with me already.

[Soundman2020]

I found a general decibel chart from GCAudio website that I'm assuming is relatively accurate for the decibel levels that we generally have (from the loudest reference point at the instruments).

Right, but that's not much good for measuring YOUR classes with YOUR teachers and YOUR students! Those are just general levels. You need an actual hand-held sound level meter to measure the levels in a couple of typical teaching sessions, inside the room, and also outside the room. Sound level meters are not expensive. You can pick up a good one on eBay or Amazon for around US$ 100. You need one that has both "A" and "C" weighting, as well as "fast" an "slow" response. If it has more than that, then great, but it must have that at least. Just don't get one of the cheap junk Chinese "toy" meters that go for US$ 25 to US$ 50.... those are useless. Get an Extech, or a Galaxy, or something decent like that.

I would love to achieve a 30 decibel level just outside the room,

That's probably unrealistic. Most meters can't even measure levels at 30 dB or lower, because they are too quiet. Most people would consider a level of 30 dB to be very, very quiet, some would cal it "total silence". That's about the level you would get inside your bedroom, late at night, in a very quiet area, with no wind or rain, no TV or radio, no fan, no air conditioning, nothing at all turned on... or the level you would get if you went out and stood in the middle of the desert, dozens of miles from nowhere, with no roads, houses, or anything nearby, on a calm windless night... In other words, 30 dB is quiet!

Check the website or your local municipality, and look for the noise regulations. They will tell you what your legal obligations are, in terms of how much noise you can make at different times of day. As long as you are within those ranges, you should be OK.

But to be certain, use your hand-held meter to check the actual real level in the area where you expect to have your studio. Just take the meter outdoors at a couple of places in that suburb, at the time of day when your students would normally be betting their lessons, and measure the general ambient noise around you. That's the level you should be aiming for in order to not disturb your neighbors, regardless of what the law says. Most municipal regulations have a clause hidden somewhere saying something like "... However, any noise that is unpleasant, disagreeable, or unwanted is also prohibited, regardless of the measured level". In other words, the "measured levels" are useless, since any inspector, cop or disgruntled municipal worker can decide that your students are making an "unpleasant" noise, even if you r levels meet the regulated standards! Nice, isn't it? But if you are as quiet as the background level, then you won't be heard at all, so that's a good level to aim for.

I would be seeking 75dB of sound isolation.

Unless you have a very substantial budget, that isn't realistic. About the maximum you can expect to achieve for a typical home studio, project studio, or rehearsal studio, is about 60 dB. Most studio builders are happy to get 50 dB. To put that in perspective, that's a hundred times better than a typical house wall, which will get you about 30 or so. A hundred times better in how much energy it stops, but only four times better subjectively. In other words, you would judge that only about a quarter as much sound is getting through, as compared to a normal house wall. If you could get 60 dB, then you'd judge that subjectively as being about one eighth the level of a typical house wall.

OK, there is some good news here: air. Air attenuates sound, and the more air you have between your studio and the neighbors, the better it is for you. Theoretically, each time you double the distance between you and your neighbors, the sound level drops off by 6 dB, but in practice it its more like 4 or 5 dB. So here's a realistic scenario: You have a practice session going on inside your room at 105 dB. You managed to get 50 dB isolation in your construction, so the level outside is 55 dB. If your student's level is 55 dB outside the walls at a distance of 3 feet, it would be 51 dB at 6 feet, 47 dB at 12 feet, 43 dB at 24 feet, 39 dB at 48 feet, 32 dB at 128 feet, etc. So if you have plenty of space around your building, then you will get the benefit of natural attenuation simply due to the distance.

Having put some thought into what you were saying about size of the rooms, I started considering building somewhat larger stand-alone units (adding a couple feet of width and length), and extending them upwards several feet, to create more open air for sound to dissipate in, and help improve internal acoustics.

Excellent! That makes sense.

Then I started considering costs, and balked a bit,

Well, there's no such thing as "cheap, good isolation"! You can have one of those two, but not the other...

and balked a bit, and reconsidered modifying our preexisting room that is 9.5 feet wide, and 17.5 feet long, with a single door close to one end of the room

With a single door, you are limited to the isolation that can be provided by... well... a single door! It doesn't matter how well you isolate the rest of the room, if you only have one typical door on it. If that is a typical hollow-core door that you buy at Home Depot, then your isolation will be around 20-something dB. That's about all you can hope for. If it is a good solid-core door with good air-tight seals all around, you could get 30-something dB of isolation out of it. But not much more. You can't expect miracles from single doors.

It has 2 layers of sheet rock on each side of the framing, contains cheap insulation that is generic to most office spaces,

That would give you roughly 35 dB of isolation, but very poor in low frequencies: down to only about 15 dB or isolation at 130 Hz, for example, since that's the resonant frequency of that wall system: it passes sound very cleanly at that frequency, almost like it wasn't there at all. 130 Hz is in the third octave of a grand piano... it's about half way up the range of a bass guitar, and in the first octave of an acoustic guitar. It is one octave down from middle C.... So any notes played in that region will shine through your walls pretty well... My guess is that you already know this, since you are already using that room!

styrofoam-like panels,

Styrofoam has no acoustical uses at all. None. (Except to make the cups that hold your coffee while you are playing... ) Styrofoam is "closed cell" insulation, meaning that air cannot penetrate into it, so it cannot absorb any sound. Proper acoustic foam is "open cell", with numerous tiny air holes riddling it. So what you have there is useless. Styrofoam is great as a thermal insulation (which is why it is good for holding your coffee!), but not at all for acoustic treatment.

One wall is up adjacent to our warehouse, and it is not at all critical to prevent sound from flooding into that space.

Fishtank. Aquarium. Imagine that you want to build an aquarium to put in your living room at home, so you can watch fish swimming around. So you go to a store and by an empty steel frame to make your tank. Then you figure that "Well, I only need to see the fish from one side, so I'll only put glass on that side of the frame: it is not at all critical for me to see the fist from the other sides, so I won't put any glass there".... I think you can imagine how well your aquarium will hold water! That's about how well a room will isolate if you only put one isolation wall on it.

But you are saying more like : "I need to see the fish from the front, left and right sides, but not from the back, so I'll put glass on front, left and right sides of the frame, but just a piece of cardboard in the back."...

Yup. that's basically what you are saying here, with the comment that you don't mind if sound "floods into that warehouse space". That's the same as saying that you don't mind if aquarium water floods out the back of your tank, since you only want to loom form the front and sides...

I think you get the picture: In order to have a fish tank that holds water, you need glass on all four sides and the top and bottom. In order to have a studio that "holds sound", you need to have isolation on all four sides and the ceiling.

It is that simple. Isolation is only as good as the weakest part. You can have the best isolated studio in the world, but if you open the door, all the sound gets out. Sound is just like water in that sense: it takes the simplest path out. And once it is out, it floods out and splashes all over, NOT just in the direction you thought it would go!

In other words; you need to isolate your practice rooms to the same level all around: walls, floor, ceiling, doors windows, HVAC vents, electrical outlets... all of it has to be done to the same level.

I am considering the option of ...

.... and that would get you about 38 dB of isolation, assuming that you did it all perfectly!

The issue is simply this: coupling. As long as the drywall on the both sides or your wall is attached to the same studs in the middle, you will NEVER get good isolation, no matter how many layers you put on each side, or what you put in the middle. The drywall on one side picks up the vibrations, causing the studs to vibrate, causing the drywall on the other side to vibrate, which acts like a huge loudspeaker. As long as the two leaves of drywall are coupled together buy the studs, you won't ever get good isolation. The solution, of course, is to break that coupling! You can do that in several ways, but for you probably the easiest is with something called RSIC clips and hat channel: Take off the drywall on one side of the studs, screw the clips into the studs at the recommended spacing, put hat channel in the clips, then put the drywall back on again. "RSIC" stands for "Resilient Sound Isolation Clips" They decouple the drywall from the studs, breaking the transmission path. Just by putting those on you can get a large jump in isolation. You could get 40 to 45 dB of isolation like that (assuming you filled the wall cavity with suitable insulation). Adding Green Glue between the layers of drywall would add another few points. You would then need to beef up your door with a lot of extra mass, put double seals all the way around it (top, bottom and both sides), put silencer boxes on your HVAC vents, put putty pads behind all of your electrical boxes, and carefully seal up all cracks, gaps and cavities all around the room, in every side.

If that's not enough, then you would need to take off the drywall as above, build a second frame an inch away from the existing frame, and put your drywall back again. That provides even more decoupling, down to lower frequencies.

I have no idea yet as to how to discern the level of sound isolation I will achieve from different materials and methods,

You could look through this document:

http://archive.nrc-cnrc.gc.ca/obj/irc/d ... /ir761.pdf

That contains laboratory tests on over 300 different walls, built in many different ways, and with different materials and techniques. But do be careful to ignore the STC ratings on each page: those are not applicable to music, only to speech. Instead, look at the graphs and the tables of numbers.

and what is the best method of laying out all of my construction, and especially am clueless about the ceilings and floors, and what doorways I should look into, especially that will provide a window for people to monitor what is happening in the rooms

Then you need two books: "Master Handbook of Acoustics" by F. Alton Everest, and "Home Recording Studio: Build it Like the Pros", by Rod Gervais. They will give you the basis of what you need to know to design your isolation system yourself.

Once you have a rough plan in place, then post it here so we can take a look at it, and let you know if it is OK, and how to improve it.

- Stuart -